> Nick Piggin <npiggin@gmail.com> writes:>>> On 2 May 2012 00:08, Jeff Moyer <jmoyer@redhat.com> wrote:>>> Nick Piggin <npiggin@gmail.com> writes:>>>>>>> Not a bad fix. But it's kind of sad to have i_size checking logic also in>>>> block_read_full_page, that does not cope with this.>>>>>>>> I have found there are parts of the kernel (readahead) that try to read>>>> beyond EOF and seem to get angry if we return an error (by not>>>> marking uptodate in readpage) in that case though :(>>>>>>>> But, either way, I think it's very reasonable to not mark buffers beyond>>>> end of device as mapped. So I think your patch is fine.>>>>>>>> I guess for ext[234], it does not read metadata close to the end of the>>>> device or you were using 4K sized blocks?>>>>>> Well, the test case just reads directly from the loop device, bypassing>>> the file system, and I did use 1KB blocks when making the file system, so>>> it is quite puzzling.>>>> It's because buffer_head creation does not go through the same paths>> for bdev file access versus getblk APIs.>>>> blkdev_get_block does the right thing there>>>> In fact, it's probably good to unify the checks here, i.e., use max_blocks()>> You really think it's worth it? I mean, it's just an i_size_read and a> shift, and there is precedent for it inside fs/buffer.c. I'd prefer to> keep the patch as-is, but will change it if you feel that strongly about> it.

Anyway, here is the other version of the patch, using max_block as yousuggested.